Law enforcement at all levels are also cleared to use DHS funds to purchase surveillance robots like this one, made by a company called Icor:

It is a weaponized surveillance robot equipped with pan-tilt-zoom cameras. The device can be manipulated from afar via internet connection. The device is large and therefore not the best choice for secret surveillance, but smaller robots exist for just that purpose. 

M-Bots, Inc. makes a robot it calls “SNEAKY“. Take a look:

Police can also buy a giant, weaponized robot capable of picking up cars. This monstrosity was made by Remotec, a division of war giant Northrop Grumman.

Among the better kept secrets on the robotics page of DHS' Responder Knowledge Base website is the “Disrupter Tool Tower”: